Barack Obama and US political leaders believe the president does not need Congress' permission to take certain measures to quell the al Qa'ida-inspired uprising sweeping through Iraq, the Senate's top Republican and others have said.

But the prospect of the president sidestepping Congress raises the potential for clashes between the White House and rank-and-file politicians, particularly if Mr Obama should launch strikes with manned aircraft or take other direct military action in Iraq.

Administration officials have said air strikes have become less a focus of recent deliberations but have also said the president could order such a step if intelligence agencies could identify clear targets on the ground.

Mr Obama huddled in the Oval Office for over an hour to discuss options for responding the crumbling security situation in Iraq with Democratic senate majority leader Harry Reid, Republican senate minority leader Mitch McConnell, Republican House of Representatives speaker John Boehner, and Democratic house minority leader Nancy Pelosi.

Speaking to reporters later, Mr McConnell said the president "indicated he didn't feel he had any need for authority from us for steps that he might take".

Ms Pelosi agreed with the president, saying in a statement after the meeting that Mr Obama did not need "any further legislative authority to pursue the particular options for increased security assistance discussed today". She did not specify what options were discussed.

An administration official said it was the leaders who suggested Mr Obama already had existing authorities to take additional action in Iraq without further congressional permission. The official downplayed the notion that the president agreed with that assessment, saying only that he said he would continue to consult politicians.

The White House has publicly dodged questions about whether Mr Obama might seek congressional approval if he decides to take military action. Last summer he sought approval for possible strikes against Syria, but scrapped the effort when it became clear that politicians would not grant him the authority.

But administration officials have suggested that the president may be able to act on his own in this case because Iraq's government has requested US military assistance.

"I think it certainly is a distinction and difference worth noting," White House spokesman Jay Carney said of the comparisons to the Syrian situation.

In addition, an authorisation for the use of military force in Iraq, passed by Congress in 2002, is still on the books and could potentially be used as a rationale for the White House acting without additional approval. Before the outburst of violence in Iraq, Mr Obama had called for that authorisation to be repealed.

Some politicians were outraged when Mr Obama launched military action in Libya in 2011 with minimal consultation with Congress and no formal authorisation from them. More recently, some in Congress have complained that the White House did not consult on final plans for releasing five Taliban detainees from Guantanamo Bay, Cuba, in exchange for freeing detained American soldier Sgt Bowe Bergdahl.

In a diplomatic tour de force, vice president Joe Biden spoke to Iraq's Shiite prime minister, its Sunni parliamentary speaker and the president of Iraq's self-ruled northern Kurdish region yesterday.

Mr Biden, who was travelling in Latin America, praised all three leaders for the participation of their respective communities in a televised show of unity against the group Islamic State in Iraq and the Levant, the White House said.

White House officials offered no timeline for how soon Mr Obama might decide on how to respond to the fast-moving militants from Isis, which has seized Mosul, Tikrit and other towns in Iraq as the country's military melted away.

Mr Obama's decision-making on air strikes has been complicated by intelligence gaps that resulted from the US military withdrawal from Iraq in late 2011, which left the country largely off-limits to American operatives.

Intelligence agencies are now trying to close gaps and identify possible targets that include insurgent encampments, training camps, weapons caches and other stationary supplies, according to US officials.

Officials also suggest that the US could more easily identify targets on the ground if Mr Obama would send in additional American trainers to work with Iraqi security forces. The president is considering that possibility, the officials say, though he has ruled out sending troops for combat missions.

Beyond air strikes, the White House has been considering plans to boost Iraq's intelligence about the militants and, more broadly, has been encouraging the Shiite-dominated government in Baghdad to become more inclusive.

Iraq's once-dominant Sunni minority has long complained of discrimination by the government and security forces. The Obama administration has said that without long-term political changes, any short-term military solutions would be fleeting.

Republicans continued to insist that Mr Obama bears the blame for allowing the insurgency to strengthen because of his decision to withdraw US forces from Iraq in late 2011 after more than eight years of war.

Washington and Baghdad failed to reach a security agreement that would have allowed American forces to stay longer.